Moving library collections: Monitoring
If everything looks like it's going absolutely on schedule and according to the plans, wait until you're about half-way through the shift to remeasure your growth space. Count the remaining shelves and redo your paper shift based on new information. This is very important. If you're off by 1/4 inch per shelf, it takes only 4 shelves to be off by an inch, 40 shelves to be off by 10 inches, 400 shelves to be off by 100 inches, etc. It can be amazing how quickly you can be off-course.>
Also, as each min-shift gets close to being done, recount the number of shelves left in that mini-shift, re-measure the space left, and recalculate the shift. This shouldn't take much time to do since the mini-shifts are so small, but it's well worth the time. If you find you'll have left-over books (not enough space) then start reducing the growth space drastically so they'll fit. I recommend letting there be some pretty tight spaces at the ends of mini-shifts rather than redoing the whole mini-shift.... you can fix the tight areas later.
Oh: remember the attitude of no-fault shifting. Mistakes happen: they're always correctable. Don't make a big deal about them.